Interposer with feedback

ABSTRACT

An optical subassembly comprising: (a) an interposer having first and second opposing sides and defining at least one alignment aperture extending from said first opposing side to said second opposing side; (b) at least one fiber having a first optical axis disposed in said at least one alignment aperture; (c) at least one optical component mounted to said second opposing side having a second optical axis coincident with said first optical axis and defining an interface between said at least one optical component and said at least one optical component; and (d) a feedback component disposed on interposer within line-of-sight of said interface to receive at least a portion of uncoupled light emitted from said interface.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/450,189, filed Jun. 24, 2019, and hereby incorporated byreference.

FIELD OF INVENTION

The subject matter herein relates generally to fiber optic interposers,and more particularly, to an interposer having optical features forpassive alignment, direct optical coupling, and integrated electronics.

BACKGROUND

Fiber optics are used in a wide variety of applications. The use ofoptical fibers as a medium for transmission of digital data (includingvoice data) is becoming increasingly more common due to the highreliability and large bandwidth available with optical transmissionsystems. Fundamental to these systems are optical subassemblies (OSA)for transmitting and/or receiving optical signals. There is an on-goingneed to provide simplified platforms for OSAs that simplify optics andpromote passive alignment while improving optical performance. Thepresent invention fulfills this need among others.

SUMMARY OF INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

In one embodiment, the invention relates to an optical subassemblycomprising: (a) an interposer having first and second opposing sides anddefining at least one alignment aperture extending from the firstopposing side to the second opposing side, the interposer definingtraces having first, second, and third contacts, the first contactsbeing configured for electrical connection to at least one opticalcomponent, the second contacts being configured for electricalconnection to at least one chip, and the third contacts being configuredfor electrical connection to a circuit board; (b) at least one fiberhaving a first optical axis, the fiber being held such that firstoptical axis is positioned essentially orthogonal to the first andsecond opposing sides; (c) the at least one optical component mounted tothe second opposing side and being electrically connected to at least aportion of the first contacts, the at least one optical component havinga second optical axis coincident with the first optical axis; (d) the atleast one chip for operating the at least one optical component, the atleast one chip being mounted on the first or second opposing side andelectrically connected to at least a portion of the second contacts; and(e) the circuit board configured to receive the interposer such that theinterposer is essentially orthogonal to the circuit board, the circuitboard being electrically connected to at least a portion of the thirdcontacts.

In another embodiment, the optical subassembly comprises: (a) aninterposer having first and second opposing sides and defining analignment aperture extending from the first opposing side to the secondopposing side, the interposer defining traces having contacts; (b) afiber having a first optical axis, the fiber being held such that firstoptical axis is positioned essentially orthogonal to the first andsecond opposing sides; (c) at least one optical component mounted to thesecond opposing side and being electrically connected to at least aportion of the contacts, the at least one optical component having asecond optical axis coincident with the first optical axis; and (d) acircuit board configured to receive the interposer such that theinterposer is essentially orthogonal to the circuit board and the firstoptical axis is essentially parallel to the circuit board, the circuitboard being electrically connected to at least a portion of thecontacts.

In another embodiment, the optical subassembly has active feedback andcomprises: (a) an interposer having first and second opposing sides anddefining at least one alignment aperture extending from the firstopposing side to the second opposing side; (b) at least one fiber havinga first optical axis disposed in the at least one alignment aperture;(c) at least one optical component mounted to the second opposing sidehaving a second optical axis coincident with the first optical axis anddefining an interface between the at least one optical component and theat least one optical component; and (d) a feedback component disposedwithin line-of-sight of the interface on the interposer to receive atleast a portion of uncoupled light emitted from the interface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows one embodiment of the interposer of the present inventioncomprising a fiber stub and an optical connector configured to receive aferrule.

FIG. 2a-2c show various embodiments of trace layouts of the interposerof the present invention.

FIG. 3 shows one embodiment of the interposer of the present inventionpackaged in a plug.

FIG. 4 shows a plug embodiment of the invention along with a socket toreceive the plug.

FIG. 5 shows the bottom side of the plug of FIG. 4.

FIG. 6 compares the optical connection between prior art OSAs involvingperiscope optics and the optical connection between OSAs comprising theinterposer of the present invention.

FIG. 7 shows another embodiment of the interposer of the presentinvention comprising axially aligned optical components.

FIG. 8 shows the optical connection between interposers of FIG. 7.

FIG. 9 shows an exploded view of the interposer embodiment of FIG. 7.

FIG. 10 shows one embodiment of preparing the interposer of FIG. 1.

FIG. 11 shows one embodiment of the optical subassembly with integratedactive feedback.

FIG. 12 shows one embodiment of the traces of the optical subassembly ofFIG. 11.

DETAILED DESCRIPTION

Referring to FIG. 1, one embodiment of an optical subassembly (OSA) 100of the present invention is shown. The OSA 100 comprises a fiber 104having a first optical axis 107 and an interposer 101. The interposerhas first and second opposing (e.g. parallel) sides 101 a, 101 b, anddefines an alignment aperture 103 extending from the first opposing sideto the second opposing side. In one embodiment, the alignment aperture103 receives the fiber and holds the fiber such that the first opticalaxis 107 is positioned perpendicular to the first and second opposingsides.

The interposer also defines traces 102 having first, second, and thirdcontacts, 202 a, 202 c, 202 b (see FIGS. 2a-2c ). Referring to FIGS.2a-2c , the first contact(s) 202 a are configured for connection to theoptical component, and, in one embodiment, are disposed about theperimeter 222 of the alignment aperture on the second opposing side. Thesecond contact(s) 202 c are configured for connection to a chip, and, inone embodiment, are disposed in the interior of the interposer. Thethird contact(s) 202 b are configured for connection to a circuit board,and, in one embodiment, are disposed about the perimeter 223 of theinterposer.

The OSA also comprises at least one optical component 106 mounted to thesecond opposing side and electrically connected to at least a portion ofthe first contacts. The optical component has a second optical axis 108coincident with the first optical axis 107 of the fiber. The fiber 104is directly coupled optically with the at least one optical component106. Referring to FIG. 2c , the OSA comprises further at least one chip221 for operating the at least one optical component 220 (106 in in FIG.1). The chip is mounted on either the first or second opposing side andis electrically connected to at least a portion of the second contacts.It should be understood that, although the second contact(s) 202 c aredepicted on the second opposing side of the interposer, if the chip weremounted on the first opposing side, then at least a portion of thesecond contacts would be disposed on the first opposing side.Additionally, in such an embodiment, the interposer may comprise viasfor connecting the traces between the first and second opposing sides.

The OSA is described below in further detail and in connection withselected alternative embodiments.

An important element of the OSA of this disclosure is the interposer. Aninterposer functions as a substrate for optical, opto-electrical, andelectrical components and provides interconnections to optically and/orelectrically interconnect the optical/opto-electrical/electricalcomponents. Although the first and second opposing sides are parallel inspecific embodiments, in other embodiments the first and second opposingsides may be non-parallel. The interposer should be rigid to support theoptical and electrical components, and capable of being readily machinedor etched. In one embodiment, the interposer comprises an insulatingmaterial to isolate electrical traces and contacts disposed thereon. Inone embodiment, the interposer comprises a ceramic or glass.Alternatively, the interposer may comprise a semiconductor such assilicon. In one embodiment, the interposer comprises a material havingessentially the same coefficient of expansion (COE) as the opticalcomponent and chip disposed thereon. (Silicon and ceramic have similarCOEs.) By matching the COE of the interposer to the components mountedthereon, the OSA is stable over a wide temperature range. This isparticularly beneficial in applications in which sterilizing the OSA maybe required such as in medical applications.

One feature of one embodiment of the interposer is an alignment apertureto align the fiber such that the fiber's optical axis is preciselypositioned in the interposer and essentially orthogonal/perpendicular tothe interposer. As used herein, the term essentiallyorthogonal/perpendicular means about 90°, not precisely 90° but forexample 90°+/−5° or so. In one embodiment, the aperture is configured tohold the fiber in a precise position relative to the interposer, therebyfacilitating passive alignment of the fiber with respect to the opticalcomponent. Passive alignment is generally preferred as it facilitatesmanufacturability (as opposed active alignment which requires energizingthe optical components and then aligning optical components to optimizeoptical coupling).

The alignment aperture may have different embodiments. For example, inFIG. 2a , the interposer is shown with a V-groove 204 a for aligning theoptical fiber. V-grooves are well-known for providing precise alignmentfor optical elements having a round cross-section such as an opticalfiber. Referring to FIG. 2b , an alternative embodiment is shown inwhich the alignment aperture is a borehole 204 b. Although the V-grooveand borehole are disclosed herein, it should be understood that otheralignment aperture configurations can be used, including, for example,any polygon shape providing at least three points of contact with thefiber (e.g., a square aperture, hexagon aperture, etc.).

In another embodiment, the alignment aperture is configured as a ferrulereceiver or as a receptacle to receive a plug containing the fiber. Inone embodiment, the first opposing side of the interposer may comprise astructure for inter-engaging mechanically with the plug. Although notshown, such a configuration may involve a ferrule receiver 118 such asthat shown in FIG. 1 (and described below) and a connector comprising aferrule from which a fiber protrudes so as to be received in thealignment aperture. Alternatively, the aperture may be configured toreceive a ferrule containing a fiber. Those of skill in the art willappreciate other suitable alignment aperture configurations in light ofthis disclosure.

In addition to the alignment aperture, other alignment features may beused such as alignment holes/alignment pins for ferrules (e.g. MTferrules) or for aligning components on/under the interposer as in knownto those of skill in the art in light of this disclosure.

Another feature of one embodiment of the invention is direct couplingbetween the optical fiber and the optical component. As used herein,direct coupling means no light bending between the optical axis of thefiber and the optical axis of the optical component. Accordingly, in adirect coupling, there are no intervening optics/reflective/refractivesurfaces to change the direction of light propagation between theoptical axis of the fiber and the optical axis of the optical component.In other words, unlike many conventional OSAs, the OSA of the presentinvention does not have reflective surfaces between the fiber and theoptical component. Such an embodiment simplifies manufacturing andprovides a more robust/high integrity optical path between opticalcomponents of different OSAs. For example, referring to FIG. 6, aconventional interconnection 601 between a transmitter 662 and areceiver 661 is shown. In this conventional interconnection, lightbending 660 is required to change the direction of light propagationfrom the optical components 612, 613 of the OSAs to the fiber 614. Theoptical axes 607, 608 of the optical components 612, 613 areorthogonal/perpendicular to the OSAs' circuit boards 610, 611 and fiber614, requiring periscope optics or light bending 660 to turn the light.No such light bending is required in the interconnection 602 of thepresent invention. Here, the transmitter 664 and the receiver 663 haveoptical components 622, 623 having an optical axis 609 which isessentially parallel to the circuit boards 620, 621 and coincident withthe optical axis of the optical fiber 615.

The direct coupling between the fiber in the optical component may havedifferent embodiments. For example, in one embodiment, the optical fiberis butt coupled to the optical component as shown in FIG. 1. A buttcoupled interface provides a high integrity/low loss optical coupling.In one embodiment, the butt coupled interface involves physicallycontacting the end face of the optical fiber with the optical component.In another embodiment, no physical contact is made between the fiber endface and the optical component, thereby defining an airgap therebetween,as shown, for example in FIG. 1. In such an embodiment, it may bebeneficial to use an antireflective coating to reduce Fresnel losses. Inyet another embodiment, it may be beneficial to use an expanded beamcoupling between the fiber and the optical component. For example, inone embodiment, a gradient-index (GRIN) lens is disposed between thefiber end face and the optical component. Alternately, a converging lensmay be formed on the fiber end face or otherwise disposed near the endface for focusing light. Still other embodiments will be known to thoseof skill in the art in light of this disclosure.

The configuration of the optical component(s) on the interposer mayvary. For example, in one embodiment, the interposer comprises just atransmit or receive optical component. In this embodiment, the OSA maybe part of a dedicated transmitter or receiver. Alternatively, theinterposer may comprise both transmit and receive optical components andthe OSA may be part of a transceiver. In this embodiment, the opticalcomponents may be disposed separately on the interposer, or, in oneembodiment, they may be disposed in series. For example, referring toFIG. 7, one embodiment of the optical components in series is shown. Inthis embodiment, the interposer 701 defines an alignment aperturethrough which optical fiber 704 is disposed. A transmitting opticalcomponent 771 is disposed adjacent the optical fiber 704. A secondoptical component, for example, a receiving optical component 772, maybe disposed on the interposer such that its optical axis is coincidentwith that of the transmitting optical component 771. In this particularembodiment, the receiving optical component 772 is behind thetransmitting optical component 771, and thus, the signal received by thereceiving optical component 772 passes through the transmitting opticalcomponent 771. This requires that the optical components be configuredsuch that the transmitting optical component is essentially transparentto the received signal. Those of skill in the art will understand how toconfigure the transmitting optical component to be essentiallytransparent to the received signal in light of this disclosure. (See,for example, FIG. 8 and associated text.)

As shown in FIG. 7, the receiving optical component 772 is mounted on asecond interposer 773. The second interposer 7073 comprisestraces/contacts 776, 777 that electrically connect the receiving opticalcomponent 772 with the traces on the interposer 701. Separate contacts778 are provided for electrically connecting the transmitting opticalcomponent 771 with its respective chip. As shown, in this embodiment, achip 774 is disposed on the substrate which can be configured to operateone or more of the optical components. The advantage of thisconfiguration is that both the transmitting and receiving opticalcomponents are disposed on a single interposer and are coupled to asingle fiber.

Referring to FIG. 9, the concept of the interposer of FIG. 7 is shown inan exploded view of OSA 900 similar to OSA 700. As shown, a transmittingoptical component 971 is disposed on interposer 901. Traces 991 connectthe transmitting optical component 971 with its associated chip 992. Thereceiving optical component 972 is disposed over the transmittingoptical component 971 and supported by the second interposer 973. Thesecond interposer 973 has an orifice 975 to accommodate/receive thetransmitting optical component 971. The second interposer 973 also hastraces 990 and vias (not shown) which are configured to interface withtraces 993 to connect the receiving optical component 972 to itsassociated chip 994. As with the other interposer embodiments, thirdcontacts 989 are disposed along the perimeter of the interposer forcontact with corresponding circuit board contacts.

The transceiver embodiment of OSA 700 simplifies installations. Forexample, referring to FIG. 8, a schematic is shown in which the OSA 700of FIG. 7 is connected to another OSA 700′ via optical fiber 704. Asmentioned above, such a connection does not require any additionaloptics/light bending to facilitate contact between optical connectionbetween the two OSAs. Moreover, the OSAs 700, 700′ facilitatebi-directional communication over a single fiber 704 according to aspecific embodiment. For example, in one embodiment, the receivingoptical components 772, 772′ of the OSAs 700, 700′ are sensitive over abroad range, which also covers the wavelength of the transmittingoptical components 771, 771′. The transmitting optical component 771,771′ transmit at different wavelengths, wherein the transmitting opticalcomponent 771 is transparent at the transmitting wavelength of thetransmitting optical component 771′, and the transmitting opticalcomponent 771′ is transparent at the transmitting wavelength of thetransmitting optical component 771. For example, in one embodiment, thetransmitting optical component is essentially transparent to receivedlight having a wavelength around 1310 nm. In this embodiment, thetransmitted signal may have a significantly shorter wavelength, e.g.,around 850 nm. This way, the receiving optical component 772 can receivethe signal from the transmitting optical component 771′, even though thetransmitting optical component 771 is right in front of it because thetransmitting optical component 771 is transparent to the signal from thetransmitting optical component 771′ (and vice versa).

Still other embodiments are possible, for example, in one embodiment,the chip is integrated with the optical component. In such anembodiment, it should be understood that there would not be any tracesbetween the optical component and the chip as shown in FIGS. 2A and 2B.

The fiber's integration into the OSA of the present invention may havedifferent embodiments. For example, referring to FIG. 1, a fiber stub isshown disposed in the borehole of the interposer. Such an embodimentfacilitates manufacturing as discussed in more detail with respect toFIG. 10.

In another embodiment, the interposer comprises a ferrule-receivingfixture disposed on the first opposing side to receive a connector 115.In one embodiment, the ferrule-receiving fixture 118, such as a fiberalignment sleeve, has an axis coincident with the first optical axis andbeing configured to receive a ferrule 116 containing a terminated fiber117 such that the terminated fiber optically couples with the fiber stubin interposer 101.

Alternatively, rather than a fiber stub, the alignment aperture may beconfigured to receive a longer length of fiber or even be configured asa connector to receive a plug. For example, referring to FIG. 7, anotherembodiment of the fiber is shown in which the interposer does not have afiber stub but instead has a longer length of a fiber that is disposedin the interposer and extends beyond the side of the interposer. Instill another embodiment, the fiber is terminated in a ferrule, which isthen disposed in the interposer. In yet another embodiment, multiplefibers may be disposed in the interposer for a multifiber connection tothe optical component(s). In this regard, although a single-fiberferrule is shown in FIG. 1, it should be understood that a multi-fiberferrule, such as the MT ferrule, may be used in the interposer of thepresent invention according to other embodiments.

In one embodiment, one end of the optical fiber extends from the firstopposing side 101 a freely. In other words, although one end of theoptical fiber may be held in a ferrule or borehole, the other endextends freely from the interposer allowing it to be bundled/routed asneed be. For example, referring to FIG. 7, the fiber 704 extends freelyfrom the first opposing side of the interposer, allowing the fiber to berouted or terminated as need be. For example, in the embodiment of FIG.8, the fiber 704 from OSA 700 is terminated in another OSA 700 asdescribed below.

The interposer of the present invention facilitates a variety ofdifferent OSA packaging configurations. First, because the opticalcomponent(s) and associated chips are disposed on an interposer and arenot distributed between an interposer and a circuit board (as istraditionally done), the interposer of the present invention tends to bemore modular, affording greater flexibility in manufacturing andpackaging configurations. For example, the interposer may be disposedessentially orthogonal/perpendicular to a circuit board or parallel tothe circuit board, depending on the application. As mentioned above, inone embodiment, the interposer comprises contacts along the perimeter ofthe interposer to facilitate connection to the circuit board. Althoughlocating the second contacts along the perimeter of the interposer ispreferred as it provides a convenient connection location to the circuitboard, it should be understood that other embodiments exist. Forexample, island type connectors can be used to connect the interposer toa circuit board.

According to specific embodiments of the invention, the OSA may beembodied as a plug as or it may be integrated in a motherboard orbackplane connector assembly. For example, referring to FIG. 3, oneembodiment of a OSA plug 300 is shown. In this embodiment, theinterposer 301 is disposed essentially orthogonal/perpendicular on aprinted circuit board 330. The fiber 333 extends from the plug such thatits optical axis is essentially parallel with the printed circuit board.As described above with respect to FIG. 6, such an embodiment simplifiesconnections between OSAs, thereby minimizing additional components andsignal losses. Referring back to FIG. 3, in this embodiment, the plugalso comprises a potting structure 332 to contain the potting materialwhich, in one embodiment, is applied over the interposer. In thisembodiment, a soft overmold 334 is also applied to the assembly tofacilitate handing and protect the circuit board. In this embodiment, aplug interface 331 is provided on the bottom of the plug. Referring toFIGS. 4 and 5, according to another embodiment, a plug assembly 400similar to the plug 300 is shown. Here, the plug 430 contains theinterposer 401 of the present invention with the fiber 703 extendingessentially parallel to the circuit board as described above. On thebottom of the plug 430 are contacts 441 a that are configured forconnection to corresponding contacts 441 b of a socket 440 as shown inFIG. 4. The socket 440 comprises circuit board contacts 442 forcontacting corresponding contacts on a circuit board. FIG. 5 shows thebottom side of plug 430 and the various traces and contacts forinterfacing with the socket 440. It should be understood that this plugembodiment is just one embodiment of many packages in which theinterposer may be used.

Referring to FIG. 10, one embodiment of the process for preparing theinterposer in FIG. 1 is shown. In step 1001, an insulating substratesuch as a ceramic wafer is provided. In step 1002, the alignmentaperture is defined in the wafer. In this particular embodiment, thealignment aperture is a borehole which may for example be drilledthrough the wafer. In step 1003, a fiber stub is inserted in theborehole. In step 1004, a fritt ring is disposed between the fiber andthe borehole to center the fiber in the borehole. In step 1005, thewafer is heated such that the fritt ring melts and flows into theborehole between the fiber and the wafer thereby holding the fiber inplace. Next, in step 1006, the fiber is polished on both sides to beessentially flush with the first and second opposing sides of the waferas shown. It should be noted that for some embodiments of theinterposer, such as shown in FIG. 7, this step 1006 could be omittedwhere the fiber stub of FIG. 1 is not applicable.

In step 1007, trace, contacts, and other features are deposited on theeither side of the wafer as shown. It should be noted that, in thisdeposition step, not only are traces/contacts for the opticalcomponents/chips deposited, but also, in this embodiment, a connectionfor the female connector 118 is defined. Having these critical elementsdefined in the same deposition process is not only efficient, but alsoimproves precision by avoiding tolerance buildup which can result frommultiple deposition steps. In step 1008, the optical components/andassociated chip are disposed on the contacts on the interposer, and aferrule-receiving structure is added to the opposite side of theinterposer. It should be understood that this is only one embodiment ofpreparing interposer of the present invention. Those of skill in the artwill appreciate many variations are possible within the scope of theinvention.

Applicant discovered unexpectedly that uncoupled light emitted at theinterface of the optical component and fiber is sufficient to monitorthe output of the optical component and provide feedback. Referring toFIGS. 1, 11 and 12, one embodiment of the optical subassembly withfeedback of the present invention is shown. The optical subassembly 1100comprises an interposer 1101 having first and second opposing sides 1101a, 1101 b (side 1101 b is facing into the page), and defining at leastone alignment aperture 1203 extending from the first opposing side tothe second opposing side. At least one fiber 104 having a first opticalaxis 107 is disposed in the at least one alignment aperture. At leastone optical component 1106 is mounted to the second opposing side 1101 band has a second optical axis coincident with the first optical axis anddefining an interface 150 between the at least one optical component andthe at least one optical component. A feedback component is disposedwithin line-of-sight of the interface to receive at least a portion ofuncoupled light emitted at the interface.

As is known, not all light being emitted from the optical component iscoupled to the fiber. For example, a portion of the periphery of thebeam from the optical component is too large to fit through the aperture1203, and, thus, is incident upon the interposer around aperture 1203,causing it to be reflected. Additionally, not all light that passesthrough aperture 1203 is optically coupled with the fiber, but rather aportion is reflected by the fiber end face (i.e., reflection loss). Thisreflection loss tends to be significant if the interface 150 has a gapas shown in FIG. 1. Thus, as used herein, the term “uncoupled light”refers to light emitted from the optical component that is not opticallycoupled with the fiber. Applicant has discovered that this uncoupledlight is sufficient for monitoring the output of the optical component.

The feedback component should be disposed preferably in line-of-sight tothe interface. As used herein, the term “line-of-sight” the means anunobstructed optical path between the interface and the light receivingportion of the feedback component. It should be understood, however,that line-of-sight does not necessarily mean a straight line. In otherwords, although line-of-sight may often be a straight line, not alloptical paths are straight lines. For example, in one embodiment, lightbending optical elements may be used to modify the optical path from asimple straight line. Such an embodiment may be preferable to avoidobstructions on the interposer. For example, if a chip is disposed onthe interposer between the optical component and the feedback componentthen light bending elements may be used to avoid the obstruction andprovide an unobstructed optical path between the interface and thefeedback component. Light bending optics elements are well-known, andinclude, for example, mirrors, prisms/refractive elements, foldedoptics, reflective surfaces, waveguides, and through-substrate vias,just to name a few.

The feedback component may be mounted to either opposing side of theinterposed. In one embodiment, the feedback component is mounted on thesecond opposing side as shown in FIG. 11. In one embodiment, thefeedback component is adjacent to the optical component as also shown inFIG. 11. Such a configuration avoids the chance of the uncoupled lightbeing obstructed by other components on the interposer. Additionally, bydisposing the feedback component relatively close to the opticalcomponent, the noise to signal ratio is reduced as will be understood bythose of skill in the art in light of this disclosure. It should beunderstood, however, that the feedback component need not be adjacentthe optical component. Indeed, Applicant has found that the feedbackcomponent may be placed anywhere on the interposer provided that it hasa line-of-sight to the interface as described above.

In one embodiment, the optical component and feedback component aresurface emitting/surface receiving optical components, respectively. Forexample, in one embodiment, the optical component is a VCSEL or LED asdescribed above, and the feedback component is a photodiode. In oneembodiment, the optical component and feedback component are positionedabove the substrate with their respective emitting/receiving surfacesfacing the interposer. In such an embodiment, it is generallypreferable, although not necessarily, for the feedback component to beelevated slightly above the surface of the interposer. For example, inone embodiment, the electrical contacts for both the optical componentand the feedback component are sufficiently thick to create a gapbetween the optical component/feedback component and the surface of theinterposer. In one embodiment, the electrical contacts comprise solderbumps or gold pumps or any other know metal or alloy pump for making anelectrical connection. Such bumps are well-known. In this embodiment,bumps not only provide an electrical connection and facilitate passivealignment (as known in the art), but also serve to elevate thecomponents above the substrate of interposer surface.

In one embodiment, one or more chips 1121 to support the opticalcomponents may be mounted to the interposer as described above. Thus,the foregoing discussion in connection with the placement of the chip onthe interposer applies equally to this embodiment. As mentioned above,in some embodiments, it may be preferable to mount the chip on thecircuit board rather than on the interposer. Such an embodiment may bepreferred in applications not requiring high switching speeds.Additionally, in one embodiment, a second chip for the feedbackcomponent may be also mounted on the interposer. Although thisembodiment is not shown in FIG. 11, its configuration will be obvious tothose of skill in the art in light of this disclosure. Generally, theresponsiveness requirements for the feedback component tend to be lessthan those of the optical component, and, thus, the proximity offeedback component to its associated chip tends not to be as critical aswith the optical component.

Referring to FIG. 12, the interposer 1201 has traces 1202 having first,second, third, and fourth contacts, 1202 a, 1202 b, 1202 c and 1202 d.The first contacts are configured for electrical connection to at leastone optical component, the second contacts are configured for electricalconnection to at least one chip, the third contacts are configured forelectrical connection to a circuit board, and the fourth contacts beingconfigured for election connection to the feedback component.

These and other advantages maybe realized in accordance with thespecific embodiments described as well as other variations. It is to beunderstood that the above description is intended to be illustrative,and not restrictive. Many other embodiments and modifications within thespirit and scope of the claims will be apparent to those of skill in theart upon reviewing the above description. The scope of the inventionshould, therefore, be determined with reference to the appended claims,along with the full scope of equivalents to which such claims areentitled.

What is claimed is:
 1. An optical subassembly comprising: an interposerhaving first and second opposing sides and defining at least onealignment aperture extending from said first opposing side to saidsecond opposing side; at least one fiber having a first optical axisdisposed in said at least one alignment aperture; at least one opticalcomponent mounted to said second opposing side having a second opticalaxis coincident with said first optical axis and defining an interfacebetween said at least one optical component and said at least oneoptical component; and a feedback component disposed on interposerwithin line-of-sight of said interface to receive at least a portion ofuncoupled light emitted from said interface.
 2. The optical subassemblyof claim 1, wherein said feedback component is adjacent to said opticalcomponent.
 3. The optical subassembly of claim 1, wherein said at leasta portion comprises light reflected from said substrate.
 4. The opticalsubassembly of claim 1, wherein said interface comprises a gap.
 5. Theoptical subassembly of claim 4, wherein said at least a portioncomprises light reflected from said fiber.
 6. The optical subassembly ofclaim 1, wherein said feedback component comprises a light-receivingsurface, said light-receiving surface facing said substrate.
 7. Theoptical subassembly of claim 6, wherein a gap exists between saidlight-receiving surface and said substrate.
 8. The optical subassemblyof claim 1, wherein said optical component and feedback component areelevated above said substrate by electrical contacts.
 9. The opticalsubassembly of claim 8, wherein said electrical contacts comprise bumps.10. The optical subassembly of claim 1, wherein said feedback componentprovides active feedback on the output of said optical component. 11.The optical subassembly of claim 1, further comprising said at least onechip for operating said at least one optical component, said at leastone chip being mounted on said first or second opposing side.
 12. Theoptical subassembly of claim 1, further comprising said at least onesecond chip for cooperating with said feedback component to provide saidactive feedback.
 13. The optical subassembly of claim 1, wherein saidinterposer has traces having first, second, third, and fourth contacts,said first contacts being configured for electrical connection to atleast one optical component, said second contacts being configured forelectrical connection to at least one chip, said third contacts beingconfigured for electrical connection to a circuit board, and said fourthcontacts being configured for election connection to said feedbackcomponent.
 14. The optical subassembly of claim 13, further comprisingsaid circuit board configured to receive said interposer such that saidinterposer is essentially orthogonal to said circuit board, said circuitboard being electrically connected to at least a portion of said thirdcontacts.
 15. The optical subassembly of claim 1, wherein said at leastone optical component is a light-transmitting component.
 16. The opticalsubassembly of claim 15, wherein said light-transmitting component is aVCSEL or an LED, and said feedback component is a photodiode
 17. Theoptical subassembly of claim 1, wherein said first optical axis ispositioned essentially orthogonal to said first and second opposingsides.